When a user wishes to access a communication service, a registration phase shall be implemented in order to check that the user has the appropriate subscription. During this registration phase, the terminal used by the user to attempt to access these services transmits a subscription identifier. This identifier is checked by a server of the communication services manager and, if the identifier is valid, the access to these services is validated.
According to a first example, such communication services are implemented in a telephony network in accordance with the GSM (Global System for Mobile communications) standard. According to the specification document “3GPP TS 03.03: Numbering, Addressing and Identification”, a mobile terminal shall register with the network by transmitting the IMSI (International Mobile Subscriber Identity) identifier. The IMSI identifier is contained in the SIM (Subscriber Identity Module) card sent to each subscriber by the mobile telephony operator and serves to identify the subscriber when accessing the mobile telephony services.
According to a second example, such communication services are telephony services implemented over the Internet, by the use of VoIP (Voice over Internet Protocol) mechanisms. The user connects to a telephony service by communicating his subscription identifier and password and, once connected, it is possible to contact him by means of the IP (Internet Protocol) address allocated to the terminal that he is using.
According to a third example, such communication services are messaging services, of the e-mail type or of the instantaneous message type. In the same way, the user connects to the service by communicating his subscription identifier and password and, once connected, it is possible to contact him by means of the messaging address, such as an e-mail address, allocated to the subscription taken out.
An identifier for the subscription taken out with the communication services manager is therefore necessary to enable the user to access these services. However, this identifier also enables tracking the communications involving the user, or even determining his position in the coverage area of the network. The user can therefore easily be the subject of telephone tapping, and/or recordings of his data exchanges, and/or monitoring of his position and/or movements, unbeknownst to him.